Chemistry Reference
In-Depth Information
2.3.2 Electrical Contacts and Characteristics
Let us now turn to the possibility of constructing electrical circuitry out of gel emul-
sions in micro-fluidic systems. The first thing we have to demonstrate is that the
aqueous droplets, which are now to be considered the 'solder points' of potential
self-assembled circuits, can be suitably connected to external leads. The setup shown
in Fig.
2.9
can indeed be used to measure the electrical properties of the membranes
spanned between adjacent droplets. Figure
2.10
a shows typical traces obtained upon
applying a square wave to a single membrane through the pipettes, which were con-
figured as Ag
AgCl
2
electrodes. Both the current and the voltage are recorded using
a standard patch clamp amplifier (HEKA, EPC 10). We clearly see the loading cur-
rent of the membrane capacitance, as well as an ohmic current persisting as long as
the voltage is applied.
/
Fig. 2.10
Electrical prop-
erties of mono-olein mem-
branes formed and suspended
in a micro-fluidic channel.
a
A square wave voltage is
applied (
top
). The current
trace (
bottom
) shows distinct
peaks indicating the charg-
ing current of the membrane
capacitance.
b
The small off-
set observed in the current
trace in
a
is plotted as a func-
tion of applied voltage. We
clearly see an ohmic behavior,
which probably stems from
ionic impurities
